There are plastic explosives, and dirty bombs, but how about thermite on a plane?

The very possibility that a terrorist could bring an easy-to-assemble thermite device on a plane and light it was real enough for the FBI to include in a recent classified assessment, which prompted the Transportation Security Administration (TSA) to issue a bulletin to its own agents in December, warning them to be on the look-out, according to a new report by The Intercept.

According to The Intercept, which obtained both the FBI assessment and subsequent TSA advisory, thermite is a mixture of rust and aluminum powder that can elude bomb detectors, and when ignited, will “produce toxic gases, which can act as nerve poison, as well as a thick black smoke that will significantly inhibit any potential for in-flight safety officers to address the burn.”

Worse, standard fire extinguishers would only exacerbate the thermite’s danger, creating toxic fumes. The results could be "catastrophic" and result "in the death of every person on board," according to the TSA advisory. According to the FBI report, thermite devices “spew molten metal and hot gases” that can potentially “burn through steel and other material” on an aircraft. The report called thermite "the greatest potential incendiary threat to aviation."

Neither the FBI nor TSA said there was a specific threat by terrorists involving thermite, and a source “with knowledge of current threats” overseas told The Intercept that extremists are currently interested in other incendiary devices that do not involve the deadly chemical combo.

In addition, while it would be difficult to spot in metal detectors, experts it would be an unwieldy weapon: a terrorist would have to bring a lot of it on board to do any real damage – which would raise suspicion -- and they would have to find a way to both place it and ignite it.

Still, TSA officials who spoke with The Intercept expressed frustration that while they were provided the intelligence, they weren’t given much guidance on what to do with it. For example, they were told they had to use a non-water or non-halon extinguisher against a thermite reaction, but offered no instructions onhow, or what to use otherwise.

Aviation officials concurred. “They say to identify something we don’t know how to identify and say there is nothing we can do,” one federal air marshal said. “So basically, we hope it’s placed somewhere it does minimal damage, but basically we’re [screwed].”

Read more from The Intercept here